dual fuel tank wiring

I have a problem understanding the wiring for the sending units on my '82 Chevy 4x4. Made a page explaining as best as I can what I am trying to do and
have two links on that page for pics.
My Haynes manual doesn't have the wiring for duel tanks and my Chiltons doesn't even have wiring diagrams at all.
Can anyone help? Gordie - Regards Gordie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri, 19 May 2006 20:32:25 -0400, The Nolalu Barn Owl <&#103&#111&#114&#100&#105&#101&#64&#110&#111&#108&#97&#108&#117&#46&#111&#110&#46&#99&#97> wrote:

LOL - Boy am I an ass. Forgot the URL
http://my.tbaytel.net/nitesky/gas_tank/index.html - Regards Gordie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
There does not appear to be enough wires there for dual tanks. I purchased an 82 GMC 3/4 ton 4wd new and it did not have dual tanks. I asked the dealer about adding the second tank and purchased a tank, sending unit, switch, and changeover valve. When you flip the switch on the dash you are not only changing the valve for the gas lines you are also changing over the return line from the engine also. From memory (no comments, this goes back 24 years) there should be one wire to each sending unit for each tank and one wire to the changeover valve. Up behind the dash these wires should terminate at the switch. From there the fuel gauge should be hooked up so that when you flip the switch the gauge is reading the proper tank. If you have access to an ohmmeter / Voltmeter you should be able to figure out the wiring. That is the best I can recall at this time. Hope it helps.
GM
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 23 May 2006 02:12:44 GMT, "GM"

Thanks for the comment. I have the fuel / return / vent lines on each side and they are hooked up. When we bought the truck only the passenger side had a gas tank and that sender wire goes to the valve - pin 1. The fitting on the end of the wire on the driver's side that physically can go to the sending unit on that tank runs along the from to the front of the truck inside a harness. There is also a wire that goes from the driver's side @ the same area as the tank sending unit and it runs over to the passenger side to pin 2 on the valve.
The hole in the dash for the switch is factory. The switch is broken and I have ordered one to pick up after work tomorrow. When the switch is installed I will connect a battery and take my multimeter for some tests.
One way or another, I will figure this out.
Thanks again. You have been more help than you probably know :)
- Regards Gordie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Try this, it is from the 86 shop manual wiring diagrahm but it may be the same.
http://members.aol.com/gfretwell/fueltank.jpg
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 23 May 2006 22:36:40 -0400, snipped-for-privacy@aol.com wrote:

Thank you so very much :) We just got the new switch today. The wiring harness and plug at the dash is intact. Got busy with a new riding lawnmower after work and had no time for the truck so will likely get to it this weekend. Will post my findings.
That wiring diagram is just what the doctor ordered.
Thanks again. Gordie - Regards Gordie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 24 May 2006 23:14:55 -0400, The Nolalu Barn Owl <&#103&#111&#114&#100&#105&#101&#64&#110&#111&#108&#97&#108&#117&#46&#111&#110&#46&#99&#97> wrote:

OK, today I had some time. Installed the battery and tried at the dash switch. - No power with the key in or out, turned on or not at any of the terminal connections. - The switch won't change the tanks (you can hear the motor) but no power may well explain THAT.
I undid the covering on the harness from the left tank to the valve on the right side and all appears well and unmodified.
I also undid some of the cover on the main harness to the front along the left frame rail and found: - One wire that has been cut off and I don't yet know what it should connect to. The meter shows no power and no continuity to ground.
Anyway, I had some animals to feed and the hoards of blackflies are now thick so I retreated to the indoors for now. - Regards Gordie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 25 May 2006 20:07:57 -0400, The Nolalu Barn Owl <&#103&#111&#114&#100&#105&#101&#64&#110&#111&#108&#97&#108&#117&#46&#111&#110&#46&#99&#97> wrote:

Man, this is bugging me but I am having fun too. Probably because this is not our primary vehicle? Anyway, I went out in the dark and retrieved the switch. Spent some time with the meter and thinking. The switch should likely be supplied with 12+ and a ground to the two middle leads. The switch only makes a connection when it is depressed fully in either direction. This changes the polarity on the other two poles from straight to reverse and back. This explains why the wires under the dash are two separate harnesses for each set of two wires. Two wires for 12+ and ground and the other two wires service pins 4 & 5 on the valve. It is the VALVE that switches the gas sending units and NOT the switch (directly). The gas gauge connects to pin 2 and pin 1 goes to the left tank sending unit while pin 3 goes to the right.
What I am missing is the connection to the left tank and power to the switch. From the wiring diagram I found which wire should go to the left tank sending unit but it is unbroken and unaltered as far forward as I can follow it along the left frame rail. The best thing to do would be to cut and splice a connection to this wire and then use a jumper to power the switch and see what happens.
The cut wire I found may not have anything to do with the gas tanks at all. Perhaps I'll find out before I finish. - Regards Gordie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 25 May 2006 23:44:47 -0400, The Nolalu Barn Owl <&#103&#111&#114&#100&#105&#101&#64&#110&#111&#108&#97&#108&#117&#46&#111&#110&#46&#99&#97> wrote:

The cut wire has continuity to pin 3 at the valve. I was able to get a connector at NAPA and can splice that on to that wire. Someone took out the driver side tank and just cut off the connector, then they tucked the wire back into the split loam. I had to dig for it. Color = pink + white just like the diagram.
No power to the switch. No continuity from the switch to the valve. Somehow I got this old body upside down and under the dash with a flashlight and followed the power harness from the switch up and tight to the underside of the dash, over the steering wheel and down the driver's door pillar to ... Two crimp connectors to nowhere. The wire stops at the crimp connectors. Have to run new wire to power and ground.
Hopefully, the valve is still in good shape :) - Regards Gordie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri, 26 May 2006 22:41:36 -0400, The Nolalu Barn Owl <&#103&#111&#114&#100&#105&#101&#64&#110&#111&#108&#97&#108&#117&#46&#111&#110&#46&#99&#97> wrote:

Thanks for the help, gfretwell,
Found the ground bulkhead near the fuse box and made the connection I needed. Tapped into a live spot on the fuse box and put a 10A fuse in line to make the power connection.
The HARDEST thing to find was this: The last owner painted the truck and since he had the engine out at the time, he unplugged everything and painted. The feed through at the firewall was left unplugged. It dangled out of sight and nobody was any the wiser. I had to follow the wires from the switch to the feed through and then figure out what was going on at the engine side.
IT WORKS!!!!!
This would have been a much harder job without the wiring diagram you supplied.
Thanks again :) - Regards Gordie
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.